How important are constraints like NOT NULL and FOREIGN KEY if I'll always control my database input with PHP?

Question

I am trying to create a column in a table that\'s a foreign key, but in MySQL that\'s more difficult than it should be. It would require me to go back and make certain changes

Answer 1

It's important to implement constraints in the database because it's impossible to predict the future! You just never know when your requirements will change.

Also consider the possibility that you may have multiple developers working on the same application. You may know what all the constraints are, but a junior developer may not. With constraints on the database, the junior developer's code will generate an error, and he'll know that something needs to be fixed. Without the constraints, the code may not fail, and the data could get corrupt.